The 3DS uses a similar data structure to the regular DS. If there are 2D images of the Pokemon used anywhere in the game, you can bet we'll be able to open that easily just by sifting through.

However, depending on how the models are done, we may not be able to view them correctly for quite some time. If there are no 2D images of the Pokemon, we'll have names/movesets/basestats but no picture. So yes and no? We'll know what the unreleased Pokemon are capable of, but not what they look like.

That is of course speaking from our current knowledge of the 3DS. We'll likely come a long way by October.